In humans, cholesterol and triglycerides are part of lipoprotein complexes in the bloodstream, and can be separated via ultracentrifugation into high-density lipoprotein (HDL), intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL) and very-low-density lipoprotein (VLDL) fractions. Cholesterol and triglycerides are synthesized in the liver, incorporated into VLDL, and released into the plasma. High levels of total cholesterol (total-C), LDL-C, and apolipoprotein-B (Apo-B, a membrane complex for LDL-C and VLDL-C) promote human atherosclerosis and decreased levels of HDL-C and its transport complex, apolipoprotein-A (Apo-A), which are associated with the development of atherosclerosis. Further, cardiovascular morbidity and mortality in humans can vary directly with the level of TC and LDL-C and inversely with the level of HDL-C. In addition, researchers have found that non-HDL cholesterol (non-HDL-C), which is determined by the subtraction of HDL-C from TC, is an important indicator of hypertriglyceridemia, vascular disease, artherosclerotic disease and related conditions. Non-HDL-C particles contain Apo-B as the membrane-complexing apolipoprotein. Although non-HDL-C is a good measure for the total amount of cholesterol present in atherogenic Apo-B-containing particles, a direct measure of Apo-B may provide a better measure of the amount of atherogenic particles per unit of serum.
Although LDL-C remains the lipid value commonly used to assess cardiovascular risk, Apo-B may better reflect lipid risk. Sniderman, Am. J. Cardiol. 90(suppl):48i-54i (2002), reviews the evidence supporting the value of Apo-B in predicting coronary artery disease risk and its superiority over calculated LDL-C levels.
Cardiovascular disease (CVD) is a broad term that encompasses a variety of diseases and conditions. It refers to any disorder in any of the various parts of the cardiovascular system, which consists of the heart and all of the blood vessels found throughout the body. Diseases of the heart may include coronary artery disease, CHD, cardiomyopathy, valvular heart disease, pericardial disease, congenital heart disease (e.g., coarctation, atrial or ventricular septal defects), and heart failure. Diseases of the blood vessels may include arteriosclerosis, atherosclerosis, hypertension, stroke, vascular dementia, aneurysm, peripheral arterial disease, intermittent claudication, vasculitis, venous incompetence, venous thrombosis, varicose veins, and lymphedema. Some patients may have received treatment for their CVD, such as vascular or coronary revascularizations (angioplasty with or without stent placement, or vascular grafting). Some types of cardiovascular disease are congenital, but many are acquired later in life and are attributable to unhealthy habits, such as a sedentary lifestyle and smoking. Some types of CVD can also lead to further heart problems, such as angina, major adverse cardiovascular events (MACEs) and/or major coronary events (MCEs) such as myocardial infarction (MI) or coronary intervention, or even death (cardiac or cardiovascular), which underscores the importance of efforts to treat and prevent CVD.
Primary prevention efforts are focused on reducing known risk factors for CVD, or preventing their development, with the aim of delaying or preventing the onset of CVD, MACEs or MCEs. Secondary prevention efforts are focused on reducing recurrent CVD and decreasing mortality, MACEs or MCEs in patients with established CVD.
MACEs include cardiac death, other cardiovascular death, MCEs (which include myocardial infarction (Ml) and coronary intervention such as coronary revascularization, angioplasty, percutaneous transluminal coronary angioplasty (PTCA), percutaneous coronary intervention (PCI) and coronary artery bypass graft (CABG)), hospitalization for unstable angina, stroke, transient ischemic attack (TIA) and hospitalization and/or intervention for peripheral artery disease (PAD).
The Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults, NIH Publication No. 02-5215 (September 2002) (also known as the “NCEP ATP III”), hereby incorporated by reference, provides recommendations for cholesterol-lowering therapy in an effort to reduce risk of CHD. In the ATP III, CHD is defined as symptomatic ischemic heart disease, including MI, stable or unstable angina, demonstrated myocardial ischemia by noninvasive testing, and history of coronary artery procedures. The ATP III indicates that LDL-C is the primary target of lipid therapy, with other lipids to be controlled including triglycerides (TG), non-HDL-C and HDL-C. Apo-B is listed as an emerging risk factor. While the ATP III was not prepared to replace LDL-C as the primary target of lipid therapy, it noted that limited epidemiological and clinical trial evidence supports Apo-B's superiority over LDL-C in risk prediction.
A guiding principle of ATP III is that the intensity of LDL-C lowering therapy is adjusted to the individual's absolute risk for CHD. Risk assessment is broken down into short term (≦10-year) and long term (>10-year) risk of CHD, and the LDL-C goals are adjusted accordingly. In addition, ATP III identifies three categories of risk for CHD that modify LDL-C goals: established CHD and CHD risk equivalents, multiple (2+) risk factors, and 0-1 risk factor. Established CHD and CHD risk equivalents include CHD, other clinical atherosclerotic diseases, diabetes mellitus, and multiple risk factors and a 10-year risk for CHD >20 percent. The major independent risk factors identified in risk factor counting include cigarette smoking, hypertension, low HDL-C, family history of premature CHD and age.
The LDL-C goals for the three categories of risk factors are as follows:
Risk FactorsLDL-C GoalCHD and CHD Risk Equivalent<100 mg/dlMultiple (2+) Risk Factors <130 mg/dl*0-1 Risk Factor<160 mg/dl*LDL-C goal for multiple risk factor persons with 10-year risk >20 percent is <100 mg/dl.
The ATP III also outlines LDL-C goals for patients based on the percentage of 10-year risk for CHD:
10-Year RiskLDL-C Goal>20%<100 mg/dl10-20%<130 mg/dl<10% and Multiple (2+) Risk Factors<130 mg/dl<10% and 0-1 Risk Factor<160 mg/dl
3-hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase inhibitors (known as HMG-CoA inhibitors, or “statins”), have been used to treat hyperlipidemia and atherosclerosis, for example. Typically, statin monotherapy has been used to treat cholesterol levels, particularly when a patient is not at an acceptable LDL-C level. Statins inhibit the enzyme HMG-CoA reductase, which controls the rate of cholesterol production in the body. Statins lower cholesterol by slowing down the production of cholesterol and by increasing the liver's ability to remove the LDL-C already in the blood. Accordingly, the major effect of the statins is to lower LDL-C levels. Statins have been shown to decrease CHD risk by about one-third. However, statins only appear to have a modest effect on the TG-HDL axis.
Marine oils, also commonly referred to as fish oils, are a good source of two omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which have been found to regulate lipid metabolism. Omega-3 fatty acids have been found to have beneficial effects on the risk factors for cardiovascular diseases, especially mild hypertension, hypertriglyceridemia and on the coagulation factor VII phospholipid complex activity. Omega-3 fatty acids lower serum triglycerides, increase serum HDL-cholesterol, lower systolic and diastolic blood pressure and the pulse rate, and lower the activity of the blood coagulation factor VII phospholipid complex. Further, omega-3 fatty acids seem to be well tolerated, without giving rise to any severe side effects.
One such form of omega-3 fatty acids is a concentrate of omega-3, long chain, polyunsaturated fatty acids from fish oil containing DHA and EPA and was sold under the trademark Omacor®, and is now known as Lovaza™. Such a form of omega-3 fatty acids is described, for example, in U.S. Pat. Nos. 5,502,077, 5,656,667 and 5,698,594, each incorporated herein by reference.
Patients with mixed dyslipidemia, hypertriglyceridemia and/or hypercholesteremia often present with blood levels of LDL-C greater than 190 mg/dl, triglyceride levels of 200 mg/dl or higher, and/or Apo-B levels of greater than 0.9 g/l. In many patients with hypertriglyceridemia, hypercholesterolemia and/or mixed dyslipidemia, the use of diet and single-drug therapy does not always decrease LDL-C, triglycerides and/or Apo-B levels adequately enough to reach targeted values. In these patients, a complementary combination therapy of a statin and omega-3 fatty acids may be desirable.
Many studies have examined the combined effects of omega-3 fatty acid and statin therapy on Apo-B levels. While most of these studies confirm that statins significantly reduce Apo-B levels, most studies also report a lack of significant further reduction of Apo-B levels with added omega-3 fatty acid treatment.
Hong et al. investigated the effects of fish oil and simvastatin in patients with coronary heart disease and mixed dyslipidemia. Patients having baseline triglyceride levels of 292.8 mg/dl or 269.5 mg/dl were initially treated with 10-20 mg/day simvastatin for 6-12 weeks. Thereafter the patients were treated with simvastatin and placebo or simvastatin and 3 g/day fish oil (Meilekang™). Combined treatment significantly reduced triglyceride levels, as compared to baseline and placebo. In addition, combined treatment numerically increased HDL-C levels, and numerically reduced LDL-C levels, as compared to baseline. However, the changes in HDL-C levels and LDL-C levels were not statistically significant. Levels of Apo-B were raised in the combined treatment group, while the Apo-B levels numerically decreased in the placebo group. Hong et al., Chin. Med. Sci. J. 19:145-49 (2004).
Contacos et al. investigated the effects of fish oil and pravastatin on patients with mixed hyperlipidemia. Patients having baseline triglyceride levels of 4.6 to 5.5 mmol/l (404 to 483 mg/dl) were initially treated for 6 weeks with 40 mg/day pravastatin, 6 g/day fish oil (Himega™, containing 3 g of omega-3 fatty acids, with an EPA/DHA ratio of 2:1), or placebo. Thereafter, all patients were treated with pravastatin and fish oil for an additional 12 weeks. Initial treatment with pravastatin significantly reduced LDL-C levels. Combined treatment of pravastatin and fish oil also significantly reduced triglyceride and LDL-C levels. However, the addition of fish oil to pravastatin monotherapy resulted in only a numerical increase in LDL-C levels, which was not statistically significant. Treatment with fish oil alone significantly reduced triglyceride levels, but increased LDL-C levels. Combined treatment for this group significantly reduced LDL-C levels, as compared to fish oil alone (but not as compared to baseline). Apo-B levels were significantly reduced with pravastatin treatment. Combination treatment with fish oil further numerically reduced Apo-B levels, however it was reported that this further reduction was not significant as compared to pravastatin monotherapy. Contacos et al., Arterioscl. Thromb. 13:1755-62 (1993).
Grekas et al. reported on the combined treatment of low-dose pravastatin and fish oil in post-renal transplantation dislipidemia. Thirty renal transplant patients with persistent hypercholesterolemia (total cholesterol >200 mg/dl) and on immunosuppressive therapy were given a standard diet for 4 weeks, followed by 8 weeks of therapy with 20 mg pravastatin. Baseline triglyceride levels at the diet stage were 184 mg/dl. This period was followed by an additional 4 weeks of standard diet, then 8 weeks of therapy with 20 mg pravastatin plus 1 g fish oil (Prolipid). Baseline triglyceride levels at the diet stage were 169 mg/dl. Apo-B levels were not significantly reduced with diet+statin therapy. However, diet+statin+fish oil was reported to significantly reduce Apo-B levels. Grekas et al., Nephron (2001) 88: 329-333. The Grekas et al. study results seem dubious, given that the study did not show a significant reduction in Apo-B levels with pravastatin therapy alone. PRAVACHOL® (pravastatin) is indicated as an adjunct to diet to reduce elevated Apo-B levels in patients with primary hypercholesterolemia and mixed dyslipidemia. Thus, the fact that the Grekas et al. study did not see significant Apo-B reduction with pravastatin makes the study results subject to doubt.
Huff et al. found that the combination of dietary fish oil and lovastatin reduces Apo-B levels in both very low-density lipoprotein (VLDL) and low density lipoprotein (LDL) fractions in miniature pigs. However, the study only compared combination treatment versus fish oil monotherapy, and did not compare combination treatment versus statin monotherapy. Huff et al., Arteroscl. Thromb., 12(8): 901-910 (August 1992).
Jula et al. studied the effects of diet and simvastatin on various serum lipids in hypercholesterolemic men. After an open placebo period, subjects were allocated to a “habitual diet” or “dietary treatment” group. The dietary treatment consisted of a Mediterranean-type diet in which no more than 10% energy was from saturated and trans-unsaturated fatty acids; cholesterol intake was no more than 250 mg/day; omega-3 fatty acid intake of plant and marine origin was at least 4 g/day, and the ratio of omega-6 fatty acids to omega-3 fatty acids was less than 4; and intake of fruits, vegetables and soluble fiber was increased. Subjects were then also allocated to receive 20 mg/day simvastatin or placebo for 12 weeks in a double-blind, crossover fashion. Subjects in the dietary treatment group and the simvastatin group had significant reductions in Apo-B levels. The interaction between the two variables was reported as significant. Jula et al., JAMA 287(5): 598-605 (2002).
U.S. Patent Application Publication No. 2003/0170643 claims a method of treating a patient, by administering a therapeutic which lowers plasma concentrations of Apo-B and/or an Apo-B-containing lipoprotein and/or a component of an atherogenic lipoprotein by stimulating post-ER pre-secretory proteolysis (PERPP).
Studies have investigated the effect of statins and Omacor® omega-3 fatty acids. For example, Hansen et al. investigated the effect of lovastatin (40 mg/day) in combination with 6 g/day Omacor® omega-3 fatty acids in patients with hypercholesterolemia. Patients having baseline triglyceride levels of 1.66 mmol/l (about 146 mg/dl) were treated with 6 g/day Omacor® for 6 weeks, followed by 40 mg/day lovastatin for an additional 6 weeks, and a combination of both Omacor® and lovastatin for a final 6 weeks. Lovastatin monotherapy resulted in significant increases in HDL-C levels, and significant decreases in triglyceride and LDL-C levels. After combination treatment, triglyceride and LDL-C levels were further significantly decreased. Apo-B levels were significantly reduced with lovastatin monotherapy, and further numerically reduced with the addition of omega-3 fatty acids, although such further reduction was not indicated as being significant as compared to lovastatin monotherapy. Hansen et al., Arterioscl. Thromb. 14(2): 223-229 (February 1994).
Nordoy et al. investigated the effect of atorvastatin and omega-3 fatty acids on patients with hyperlipemia. Patients having baseline triglyceride levels of 3.84 mmol/l (about 337 mg/dl) or 4.22 mmol/l (about 371 mg/dl) were treated with 10 mg/day atorvastatin for 5 weeks. Thereafter, for an additional 5 weeks, atorvastatin treatment was supplemented with 2 g/day Omacor® or placebo. Atorvastatin monotherapy, significantly increased HDL-C levels, and triglyceride, LDL-C and Apo-B levels significantly decreased, as compared to baseline. Combination treatment further increased HDL-C levels, as compared to atorvastatin alone. Triglyceride, LDL-C and Apo-B levels numerically further declined slightly with combination treatment, as compared to atorvastatin monotherapy; however, the decrease was not significant. Nordoy et al., Nutr. Metab. Cardiovasc. Dis. (2001) 11:7-16.
Chan et al. studied the combined treatment of atorvastatin (40 mg/day) and 4 g/day 4 Omacor® on obese, insulin-resistant men with dyslipidemia studied in a fasted state. Patients having baseline triglyceride levels of 1.7 to 2.0 mmol/l (about 150 to 170 mg/dl) were treated for 6 weeks with: 40 mg/day atorvastatin and placebo; 4 g/day Omacor® and placebo; a combination of atorvastatin and Omacor®; or a combination of placebos. Atorvastatin monotherapy significantly decreased Apo-B levels. Combination treatment also significantly decreased Apo-B levels, as compared to the placebo group. However, the effects attributable to the Omacor® were not significant. Chan et al., Diabetes, 51: 2377-2386 (August 2002).
Nordoy et al. investigated the effectiveness of combination treatment of 40 mg/day lovastatin and 6 g/day Omacor® (identified as “K-85”) in patients with familial hypercholesterolemia, but who were without cardiovascular disease. The study included three intervention periods, each 6 weeks long, interrupted by washout periods of 6 weeks. The final test was carried out 12 weeks after the last intervention. Apo-B levels numerically reduced slightly with omega-3 fatty acid monotherapy, and were significantly reduced with lovastatin monotherapy. The combination treatment also significantly reduced Apo-B levels, as compared to baseline. However, the reduction was not indicated as being significant as compared to lovastatin monotherapy. Nordoy et al., Essent. Fatty Acids Eicosanoids, Invited Pap. Int'l Congr. 4th, 256-61 (1998).
Nordoy et al. also investigated the efficiency and the safety of treatment with simvastatin and omega-3 fatty acids in patients with hyperlipidemia. Patients having baseline triglyceride levels of 2.76 mmol/l (about 243 mg/dl) or 3.03 mmol/l (about 266 mg/dl) were treated for 5 weeks with 20 mg/day simvastatin or placebo, then all patients were treated for an additional 5 weeks with 20 mg/day simvastatin. Thereafter, patients were additionally treated with 4 g/day Omacor® or placebo, for a further 5 weeks. The administration of omega-3 fatty acids with simvastatin resulted in moderate reductions in serum total cholesterol and reduction in triglycerol levels, and a small numerical decrease in Apo-B levels. However, the effect attributable to the omega-3 fatty acids was not significant. Nordoy et al., J. of Internal Medicine, 243:163-170 (1998).
Durrington et al. examined the effectiveness, safety, and tolerability of a combination of Omacor® omega-3 acids and simvastatin in patients with established coronary heart disease and persisting hypertriglyceridemia. Patients having an average baseline triglyceride level >2.3 mmol/l (average patient serum triglyceride level was 4.6 mmol/l in the Omacor® group), were treated with 10-40 mg/day simvastatin (average dose in the Omacor® group was 33.3 mg/day) and 4 g/day Omacor® (2 g twice a day) or placebo, for 24 weeks in a double-blind trial, after which both groups were invited to receive Omacor® for a further 24 weeks in an open study. Combination treatment significantly decreased triglyceride levels within 12 weeks, as compared to baseline monotherapy. In addition, the VLDL cholesterol levels in these patients decreased by 30-40%. LDL-C levels significantly decreased, as compared to baseline monotherapy, only after 48 weeks, although there was a numerical (statistically insignificant) decrease at 12 and 24 weeks. Apo-B levels showed a slight numerical (statistically insignificant) decrease with addition of omega-3 fatty acids to simvastatin monotherapy. Durrington et al., Heart, 85:544-548 (2001).